1. Field of the Invention
The present invention relates generally to improvements in the electrical current transfer device for transferring electrical current between relatively rotatable members, the broad class of such devices generally being referred to as slip rings. Specifically, the invention relates to an improved current transfer device for conducting currents between stator and rotor members, such as between the relatively rotatable members utilized in aerospace applications which require the reliable and long life expectancy transfer of electrical currents from a large number of circuits across a relatively short distance measured along the axial length of the relatively rotatable members.
2. Description of the Prior Art
Rolling electrical conductor assemblies are not broadly new and have heretofore been proposed for use in place of the more conventional slip ring and brush assemblies. For example, U.S. Pat. No. 4,098,546 issued to the Applicants' assignee, discloses a full rotational freedom, substantially zero friction electrical conductor assembly for conducting electrical currents between relatively rotatable members of sensitive instruments such as gyroscopic devices and the like. Each electrical transfer unit of the assembly comprises a pair of coaxial, concentric, coplanar continuous, concave conductor rings, one mounted on a relatively fixed member and the other mounted on a rotatable member, the relative diameters of the rings providing a substantial annular radial gap therebetween. A resilient electrically conducting continuous, filamentary loop is disposed in the radial gap such that its generally flat outside surface contacts and rolls on the concave surface of the conductor rings. The loop or conductor interface provices self-capturing and retaining forces to accommodate any misalignment between the rings and movements of the loops within the radial gap in a vibratory and/or shock environment, all without producing frictional torques on the rotatable member.
The major disadvantage of the above described invention is that only a limited number of electrical currents can be transferred across a relatively short distance measured along the axial length of the relatively rotatable members. When the axial length is increased to accommodate a larger number of circuits that require electrical currents to be transferred between the relatively rotatable members, the increased length induces thermal and vibratory problems which result in a bulky, difficult to assemble, and possibly unstable structure unsuited for many environments. All known prior art attempts to solve the problem of the transfer of electrical current from high density electrical circuits between relatively rotatable members have been unsuccessful or have concentrated on increasing the axial length of the relatively rotatable members. In addition to the volumetric problems associated with the transfer of electrical current from high density electrical circuits between relatively rotatable members, there is also a need for an extremely dependable and an environmentally sound device which can operate efficiently under the adverse conditions which are common in aerospace and satellite applications. Facilitation of repairs as well as reliability are characteristics which are needed. Therefore, there is a need to provide the aerospace industry with a solution to the problem of the transfer of electrical currents from high density electrical circuits across relatively rotatable members such that efficient and reliable operation of satellite structures and/or sensitive instruments, such as gyroscopic devices may be provided under sometimes harsh environmental conditions characteristic of aerospace applications. The practice of the present invention can provide the aerospace industry with an environmentally rugged electrical conductor assembly which can efficiently transfer electrical currents from as many as 200 circuits across a distance of 13 inches measured along the axial length of the relatively rotatable members.